Comment 23 for bug 31915

sorry for the noise ... but I have to report additional findings as the
patch above really has some side-effects.

The previous version of my patch opened the /boot/grub/defaults file in
"r+" mode so I could read the initial values, do a "rewind(fp)" and
write the new values. Unfortunately the "grub-reboot" script keeps to
append new comments and disclaimer lines, effectively making the file
grow and grow.

So the only thing that really works here is to open the file read-only,
read the initial values, then close it and reopen it in "w" mode which
truncates it to zero before we write to it. Now we write the new "x:y"
values and let the script to its job of adding comment lines and
disclaimers.

Also, the original code added a newline where "grub-set-default" didn't
have one. Not a big deal, shouldn't change the functionality but it
isn't the same layout as before anymore.

To make a long story short, here is a new patch which *should* do the
job now as expected:

--- builtins.c.orig 2007-01-28 16:46:18.000000000 +0100
+++ builtins.c 2007-01-28 21:25:29.000000000 +0100
@@ -3574,16 +3574,17 @@
    default_file[i] = 0;
    grub_strncat (default_file + i, "default", DEFAULT_FILE_BUFLEN - i);

- if(!(fp = fopen(default_file,"w")))
+ if(!(fp = fopen(default_file,"r")))
      {
        errnum = ERR_READ;
        goto fail;
      }

- read(&line, -1);
-
+ fgets(line, bytes, fp);
+ fclose(fp);
+
    sscanf(line, "%d:%d", &curr_prev_default, &curr_default);
-
+
    if(curr_default != -1)
      new_prev_default = curr_default;
    else
@@ -3595,10 +3596,16 @@
      }

    if(once_only)
- sprintf(buf, "%d:%d\n", new_prev_default, new_default);
+ sprintf(buf, "%d:%d", new_prev_default, new_default);
    else
- sprintf(buf, "%d\n", new_default);
-
+ sprintf(buf, "%d", new_default);
+
+ if(!(fp = fopen(default_file,"w")))
+ {
+ errnum = ERR_READ;
+ goto fail;
+ }
+
    fprintf(fp, buf);

  fail:

--
Friedemann Baitinger <email address hidden>